The role of lysosomes in circulatory shock

An effective FRET-based two-photon ratiometric fluorescent probe with double well-resolved emission bands for lysosomal pH changes in living cells and zebrafish

In cells, lysosome is an acidic organelle (approximately pH 4.5-5.5), whose pH changes plays a key role in mediating various biological processes. To address this issue, a lot of fluorescent probes have been developed and prepared for tracking lysosomal pH changes. However, few of these probes can realize the imaging of lysosomal pH changes in biosystems. Herein, a new two-photon (TP) ratiometric fluorescent probe (NpRhLys-pH) by adopting the fluorescence resonance energy transfer (FRET) strategy has been developed for imaging of lysosomal pH changes in living cells and zebrafish. In this probe NpRhLys-pH, constructed by conjugating a TP fluorophore (D-Π-A-structured naphthalimide derivative) with a rhodamine B fluorophore via a non-conjugated flexible linker, the morpholine moiety serves as a targeting unit for anchoring lysosomes, and the xanthane derivative shows a pH-modulated open/close form of the spirocycle. Such a scaffold affords the NpRhLys-pH is a reliable and specific probe for anchoring lysosomes in living cells and zebrafish with dual-channel emission peaks separated by 85 nm, and responds to lysosomal pH rapidly and reversibly with high selectivity and sensitivity, demonstrating it can be used as a powerful tool for the biological research of the relationship between physiology and pathology and lysosomal pH changes in biological systems.

Pulmonary vascular clearance of harmful endogenous macromolecules in a porcine model of acute liver failure

BACKGROUND

Pulmonary complications are common in acute liver failure (ALF). The role of the lungs in the uptake of harmful soluble endogenous macromolecules was evaluated in a porcine model of ALF induced by hepatic devascularization (n = 8) vs. controls (n = 8). In additional experiments, pulmonary uptake was investigated in healthy pigs. Fluorochrome-labeled modified albumin (MA) was applied to investigate the cellular uptake.

RESULTS

As compared to controls, the ALF group displayed a 4-fold net increased lung uptake of hyaluronan, and 5-fold net increased uptake of both tissue plasminogen activator and lysosomal enzymes. Anatomical distribution experiments in healthy animals revealed that radiolabeled MA uptake (taken up by the same receptor as hyaluronan) was 53% by the liver, and 24% by the lungs. The lung uptake of LPS was 14% whereas 60% remained in the blood. Both fluorescence and electron microscopy revealed initial uptake of MA by pulmonary endothelial cells (PECs) with later translocation to pulmonary intravascular macrophages (PIMs). Moreover, the presence of PIMs was evident 10 min after injection. Systemic inflammatory markers such as leukopenia and increased serum TNF-α levels were evident after 20 min in the MA and LPS groups.

CONCLUSION

Significant lung uptake of harmful soluble macromolecules compensated for the defect liver scavenger function in the ALF-group. Infusion of MA induced increased TNF-α serum levels and leukopenia, similar to the effect of the known inflammatory mediator LPS. These observations suggest a potential mechanism that may contribute to lung damage secondary to liver disease.

Acute pancreatitis associated with viral hepatitis: a report of six cases with review of literature

Association of hepatitis viruses with acute pancreatitis in the setting of nonfulminant viral hepatitis is rare. We report six cases of nonfulminant viral hepatitis complicated by acute pancreatitis, including the first documented case of hepatitis E virus (HEV) associated acute pancreatitis. The other five patients had acute viral hepatitis caused by hepatitis A infection. Besides features of viral hepatitis, the presence of typical abdominal pain, high serum amylase, and ultrasound or CT scan features suggested the diagnosis of acute pancreatitis. This complication generally developed in the initial phase of the hepatitic illness. All of the patients had mild to moderate pancreatitis that recovered uneventfully with conservative treatment.

Significance of thromboxane A2 and prostaglandin I2 in acute necrotizing pancreatitis in rats

Plasma thromboxane concentrations were found to be significantly elevated in acute necrotizing pancreatitis in rats, whereas prostaglandin I2 levels were not. The significance of these alterations was investigated. Pancreatitis was induced by injecting 5% sodium taurocholate into the pancreatic duct. Iloprost (ZK 36374, a stable analog of prostaglandin I2, 25 ng/kg body weight) decreased the mortality rate from 100% to 50%. When treatment with iloprost was combined with simultaneous administration of either Sibelium (flunarizine R 14,950, 0.2 mg/kg body weight) or dazmegrel (UK 38,485, 50 mg/kg body weight) an additional decrease in the mortality rate was recorded. Dazmegrel is a selective thromboxane A2 synthetase inhibitor and flunarizine (a calcium entry blocker) also inhibits the effects of elevated thromboxane A2 levels. With flunarizine and iloprost the mortality rate was 40% (P less than 0.05); with dazmegrel and iloprost it was 10% (P less than 0.01). The results of the present study suggest that thromboxane A2 and prostaglandin I2 play a role in the course of acute necrotizing pancreatitis.

Thromboxane as a possible hepatotoxic factor increased by endotoxemia in obstructive jaundice

In a study using rats, we investigated whether liver damage induced by endotoxemia in obstructive jaundice is associated with thromboxane (TX) in order to acertain whether its vasoconstrictive and platelet aggregating properties play a role in reducing liver blood flow. The rats were divided into the following 5 groups; a control group, an endotoxin (Et) group, a bile duct ligation (BDL) group, a bile duct ligation and endotoxin (BDL + Et) group and an OKY046 (Thromboxane synthetase inhibitor) treated bile duct ligation + endotoxin (OKY-BDL + Et) group. The blood TXB2 levels in the Et, BDL and BDL + Et groups were higher than those in the control group. The liver TXB2 levels in the Et and BDL + Et groups were also higher than those in the control group. Liver phospholipids and liver blood flow decreased in the BDL + Et group, whereas in the OKY-BDL + Et group they returned close to the control group levels by decreasing the TXB2 levels in both the liver and blood to normal. These results suggest that the high level of TX in the blood and liver tissue may further aggrevate the liver during endotoxemia in obstructive jaundice by inhibiting liver blood flow.

Frequency of pancreatitis in fulminant hepatic failure using isoenzyme markers

Evidence of acute pancreatitis was sought in 35 patients with fulminant hepatic failure. Total amylase was raised in 22 patients and isoenzyme separation showed a distinct P3 isoenzyme (indicative of pancreatitis) in 14. In four patients with marked hyperamylasaemia (greater than 1000 U/l) the predominant isoenzyme was the salivary fraction. Pancreatic lipase was abnormally raised (greater than 200 U/l) in 34 patients but exceeded 1000 U/l in 12 of the 14 with a distinct P3 isoenzyme. Thus on the basis of a distinct P3 isoenzyme of amylase and an increased pancreatic lipase activity evidence of pancreatitis was found in 34% of patients in this series.

Physiology of the potentiation of lethal endotoxin shock by streptococcal pyrogenic exotoxin in rabbits

Streptococcal pyrogenic exotoxin (SPE) dramatically potentiates the lethal shock induced by gram-negative bacterial endotoxin. To provide further understanding of the mechanism underlying the potentiating effect, the physiological basis for the toxic synergism of the two toxins was investigated. Pretreatment of rabbits with an intravenous (i.v.) dose (10 micrograms/kg of body weight) of SPE greatly enhanced the endotoxin lethality and reduced the 50% lethal dose to less than 5 micrograms of endotoxin per kg. The SPE pretreatment dose caused severe pathophysiological changes in combination with a small i.v. dose of endotoxin (1 microgram/kg). These changes included transient hyperglycemia followed by profound hypoglycemia, elevation of the blood lipoperoxide level, and an acute increase in plasma beta-glucuronidase activity. These changes were comparable with those in animals given a large i.v. dose of endotoxin (100 micrograms/kg) alone. An injection of SPE alone did not alter any of the parameters described above. These results suggest that SPE renders rabbits more sensitive to extensive pathophysiologic effects of endotoxin, and the potentiating effect on endotoxin lethality may thus involve a general potentiation of physiologic failures. The SPE pretreatment depressed the vascular clearance of a large dose of endotoxin (100 micrograms/kg) but failed to affect that of a small dose of endotoxin (1 microgram/kg). The data suggest that the potentiating effect is not readily explained solely on the basis of the decreased clearance of endotoxin.

Biological time-related changes in tolerance of male mice to hypoxia--II. Circadian rhythm of lysosomal susceptibility to hypoxia

Circadian variations of mouse liver, brain and heart lysosomal susceptibility to hypoxia were investigated. Lysosomal disruption during hypoxia was estimated on the basis of the following measurements: changes in percentage free activity of beta-galactosidase and acid phosphatase, tissue loss of both lysosomal enzymes and accumulation of serum beta-galactosidase. When exposure to hypoxia took place at the end of the rest phase or at the beginning of the active phase, it was accompanied by maximum increase of percent free activity. This, presumably represents a diffusion of enzymes from lysosomes due to altered membrane permeability. However, hypoxia when occurring during the second part of the active phase and first part of the rest phase resulted in tissues loss of lysosomal enzymes and accumulation of serum lysosomal enzymes. This is believed to represent the release of lysosomal enzymes in bulk from damaged or ruptured lysosomal membranes.

Mitochondrial function in shock

Studies utilizing animal models of circulatory shock have revealed mitochondrial structural and functional damage in the liver, kidney, and brain. Adenosine triphosphate (ATP) synthesis and calcium transport rates of these mitochondria decline significantly during circulatory shock. The specific enzyme functions affected deleteriously by low flow states are the ATP synthetase, adenine nucleotide translocase, and carrier-mediated calcium transport. Other cellular alterations that possibly are responsible for, or are related to, the shock-induced mitochondrial deterioration are discussed. Differences in the mitochondrial responses to endotoxemia and hyperdynamic sepsis are described. Data are presented on the beneficial effects of early glucocorticoid treatment in prevention of mitochondrial functional deterioration during endotoxemia.

The renal lysosomes in acute experimental pancreatitis in dogs treated with prostacyclin (PGI2)

The inflammatory process in pancreas affects the function and structure of kidneys both by enzymatic toxemia and impairment of the renal circulation. In this study the stability of renal lysosomes in AEP in dogs treated with cytoprotective agent PGI2 was investigated. AEP was induced by injection of the bile and trypsin into the pancreatic duct; experiments were terminated after 12 hours. In lysosomal enriched subfraction of the kidney cortex (sedimenting in 15 000 x g) in untreated group (N = 5) relative free activity (r.f.a.) of cathepsins (Cs), acid phosphatase (APh) and beta-glucuronidase (BG) increased to 51,67 and 62% respectively, whereas in healthy dogs (N = 6) these activities were 20,38 and 25%. In dogs (N = 6) treated with PGI2 at the dose of 20 ng/kg/min. during 12 hrs, the r.f.a. of Cs, APh and BG was 18,40 and 49%, whereas in dogs (N = 5) additionally pretreated during 1 hr before induction of AEP with the same dose of PGI2, its values achieved 19,40 and 47% respectively. Our results suggest the stabilizing effect of PGI2 on kidney lysosomes damaged in acute experimental pancreatitis in dog. As possible mechanisms of prostacyclin action are discussed: limitation of necrotic process in the pancreas; improvement of renal haemodynamics; direct cytoprotective effect on the kidney.

Plasma acid phosphatase levels in endotoxaemia: modification by drugs and chemically detoxified endotoxins

The ability of chemically detoxified E. coli endotoxins and membrane-active agents to modify the toxicity of native E. coli endotoxin in vivo was examined. The time- and dose-dependent increase in plasma acid phosphatase activity following toxin administration to rats provided a convenient quantitative measure of in vivo toxicity under various experimental conditions. Treatment of endotoxin with either sodium hydroxide or sodium periodate produced substances which, when injected alone, failed to cause an increase in plasma acid phosphatase activity. When given before native endotoxin, periodate-detoxified toxin produced a dose-dependent reduction in the elevation of plasma enzyme activity caused by unmodified toxin. Pretreatment with pranolium, hydrocortisone or (+)-propranolol also reduced the in vivo toxicity of endotoxin. Mortality studies in mice provided further independent support for the effectiveness of periodate-detoxified endotoxin and membrane-active drugs as endotoxin antagonists. Evidence has been found that under certain conditions gentamicin may act synergistically with bacterial endotoxins in vivo.

Lysosomal hydrolases of dog kidney in superior mesenteric artery occlusion (SMAO) shock

In 6 dogs with superior mesenteric artery occlusion (SMAO) shock and in 6 healthy animals the total and free activity of lysosomal hydrolases (acid phosphatase, betaglucuronidase and cathepsins) in the whole homogenate, the lysosomal enriched subfraction and the supernatant of kidneys were estimated. Statistically significant differences between the two groups were not observed. These results indicate that in SMAO shock, the stability of kidney lysosomes is well preserved during observed period.

Circulating lysosomal enzymes and acute hepatic necrosis

The activities of the lysosomal enzymes acid and neutral protease, N-acetylglucosaminidase, and acid phosphatase were measured in the serum of patients with fulminant hepatic failure. Acid protease (cathepsin D) activity was increased about tenfold in patients who died and nearly fourfold in those who survived fulminant hepatic failure after paracetamol overdose, whereas activities were increased equally in patients with fulminant hepatic failure due to viral hepatitis whether or not they survived. A correlation was found between serum acid protease activity and prothrombin time, and the increase in cathepsin D activity was sustained over several days compared with aspartate aminotransferase, which showed a sharp early peak and then a fall. Circulating lysosomal proteases can damage other organs, and measurement of their activity may therefore be of added value in assessing prognosis in this condition.